Replacement DHD QuestionGeneral

i have had my dhd for about 3 weeks now and the sim cover has never fitted properly and now its getting very loose. i phoned vodafone earlier and they agreed to replace straight away and are sending a new one via courier on tuesday. my current dhd is unlocked and unbranded and i told vodafone i will not accept a locked or branded phone. my question really is am i being unfair on vodafone by demanding unlocked and unbranded and what are my chances of this actually happening. also if vodafone cannot supply a phone as requested what are my rights to refuse and request an altenative handset.
sorry for the long post and thanks in advance for your help.